Burner control apparatus



June 5, 1956 MARSHALL ET AL 2,748,345

BURNER CONTROL APPARATUS Filed April 25, 195-3 SWITCH STOP 75 RUN I START INVENTORS' WILLIAM E. MARSHALL WILLIAM J. ROBINSON CIO 5508303 A TTO/"Y/VE) United States Patent BURNER CONTRQL APPARATUS William E. Marshall, Minneapolis, and William J. Robin- 5011', Ricllfield, Minn, assignors to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application April 23, 1953, Serial No. 350,602

12 Claims. (Cl. 158-28) This invention relates to a program burner control apparatus having a motor driven timer controlling a plurality of switches in a predetermined sequence and having an electronic flame detector and a main burner control relay so interconnected as to give maximum safe operation of the fuel burner that the apparatus may be controlling.

Prior program burner control apparatus have not provided a means to check the proper operation of the flame detector and have not provided means controlled by the motor driven timer and by the main burner control relay to insure that failure of the flame detector during standby will prevent energization of the fuel burner. Also, prior program burner control apparatus have not provided means to simulate flame during standby, to thereby check the ability of the flame detector to sense the presence of flame, and to subsequently, upon a need for operation of the fuel burner, cease such simulation of flame to check the ability of the flame detector to sense the absence of flame before allowing the timer to be energized and thereby subsequently allow control of the fuel burner.

It is therefore an object of the present invention to provide an improved program burner control apparatus wherein a main control means, a flame detector, and a sequence timer are so interconnected that extremely safe operation of the burner unit is accomplished.

It is a further object of the present invention to provide a program burner control apparatus wherein upon no need for operation of the fuel burner a flame is simulated to cause a flame detector to move to the position indicative of the presence of flame and thereby condition control means to be energized upon a need for operation of the fuel burner, the energization of the control means preventing continued simulation of flame to allow the flame detector to move to the position indicative of the absence of flame, the flame detector in the last named position and the control means in energized position completing an energizing circuit for a program timer capable of controlling the burner to establish flame at the burner.

It is an object of the present invention to provide an improved program burner control apparatus having a timer and having a flame detector which is in the position indicative of flame when the apparatus is in standby condition, the flame detector in the last named position conditioning a power failure means to be energized upon a call for operation of the fuel burner to thereby cause the flame detector to assume a position indicative of no flame and thereby start the timer, the operativeness of the flame detector to detect the presence or absence of flame being initially dependent upon the timer being in the start position and later being dependent upon continued energization of the power failure means.

It is a further object of the present invention to provide an improved program burner control apparatus havinga flame detector, a control relay, and a program timer with circuitry such that the flame detector is rendered operative to detect the presence or absence of flame only when the program timer is in the start position or when the control relay is energized, with means including the control relay in deenergized position to simulate flame, with means including the flame detector in the position indicative of flame to energize the control relay upon the need for operation of the fuel burner controlled, and with means to energize the program timer when the flame relay returns to the position indicative of the absence of flame in response to the control relay being energized.

These and other objects of the present invention will be obvious upon the consideration of the accompanying specification, drawings, and appended claims.

Figure 1 is a schematic showing of the improved program burner control apparatus; and

Figure 2 is a diagram showing by means of bars the time interval in which the motor driven switches of Figure 1 are in the closed position.

Referring to Figure 1, the burner unit being controlled is shown at 10 as having a main blower motor 11, a main fuel valve 12, a pilot fuel valve 15, an ignition transformer 14, a photoelectric cell 16 positioned to detect main burner flame, and a flame rod 116 positioned to detect pilot flame.

The burner unit 10 is controlled by the improved program burner control apparatus having a main control relay 17, a timer motor 18, and an electronic flame detector 19. Power is supplied to the program burner control apparatus through power lines 20 and 21, with the supply of power being controlled by master sw' ch 22, limit switch 23, stop button 24, and start button 25. Limit switch 23 may, for example, be a control of the type which senses the temperature of the medium heated by burner unit 10 to open circuit the circuits associated with the limit switch 23 when this temperature exceeds a given value.

Referring now to the control relay 17, this relay has a winding 26, and movable switch blades 27, 28, 29, 30 and 31. The switch blades 27 through 31 are biased by means not shown to assume the deenergized position shown in Figure 1 when the relay winding 26 is deenergized. In the deenergized position the movable switch blades 27 and 31 engage the fixed contacts 32 and 33 respectively. When the movable switch blades of relay 17 move to the energized position the blades 27 through 31 engage the contacts 34, 35, 36, 37 and 38 respectively.

The timer motor 18 is shown in box form and may be any standard electric motor, for example a Telechron synchronous motor of the type used in electric clocks. Timer motor 13 is eilective to control control switches C1 through C10. For example, this timer motor 18 may be mechanically coupled to a plurality of cams, not shown, which control switches C1 through C10 in the sequence shown in Figure 2. For the sake of simplification, the mechanical connection between the timer motor and the cams, and the mechanical construction of the switches C1 through C10 is represented as being within the broken line 39.

The operation of the timer motor 18 and associated switches will be clear upon reference to Figure 2. For example, Figure 2 shows that with the timer motor in the start position switches C1, C2, and C9 are closed. In Figure 1 these switches C1, C2, and C9 are shown in the closed position. After approximately two seconds of operation of timer motor 18 the diagram of Figure 2 shows that the switches C3, C4, C8 and C10 move to the closed position. Therefore, the switches C3, C4, C8 and C10 of Figure 1, shown in the open position, will be considered to be in the closed position after the timer motor 18 has run for approximately two seconds.

Referring now to the electronic flame detector 19, this flame detector is basically of the type shown in the Richard S. Fiegal Patent 2,556,961. This electronic flame detector has a first stage 40 and a second stage 41. Electrical power is furnished to the electronic flame detector 19 by means of a transformer 42 having a primary winding 43, a high voltage secondary winding 44, a high voltage secondary winding 201i, and a low Voltage filament winding 45.

In the manner disclosed in the above mentioned Richard S. Fiegal patent, when photocell 16 located at the burner unit 1%) is subjected to the light produced by the main burner flame, a bias voltage is developed for the first stage 4'0 to render this stage substantially nonconductive. Also, upon the absence of flame at the burner unit the first stage 41) is rendered conductive. The electrical current conducting path for the first stage 40 can be traced from the left hand terminal of secondary 200 through a resistor 46, stage 40, a resistor 47, and conductor 50 to the right hand terminal of secondary 200. From this above traced circuit it can be seen that the voltage normally present across the resistor 47 due to conduction of the first stage 40 is such that the top terminal of resistor 47 is negative with respect to the bottom terminal.

Considering the apparatus of Figure 1 with the relay 17 deenergized, which is the standby condition of the apparatus when there is no need for operation of the burner unit 10, with movable switch blade 27 of relay 17 in the deenergized position to engage contact 32 a shunt circuit can be traced which shorts out resistor 47. This circuit can be traced from the lower terminal of resistor 47 through conductor 48, conductor 52, movable switch blade 27 and contact 32 of relay 17, conductor 54, and conductor 55 to the upper terminal of resistor 47. Resistor 47 is in the current conducting path of the first stage 40 and it is the voltage developed across this resistor 47 which controls the second stage 41 in accordance with the absence or presence of flame at the burner unit 10 as sensed by photocell 16 and flame rod 116. The polarity of this voltage is such that the second stage 41 is biased to be non-conductive when flame is not detected and first stage 40 i in a conductive state.

In the standby condition of the apparatus, which is the condition of the apparatus when there is no call for operation of the burner unit 16, no flame is present at the burner unit. The photocell 16 senses this absence of flame and the first stage 411 of the electronic flame detector 19 is rendered conductive. A voltage normally would be developed across resistor 47 to render the second stage 41 non-conductive. However so long as the main relay 17 is in the standby condition, resistor 47 is short circuited and therefore the second stage 41 is rendered conductive. The electrical current conducting path for the second stage 41 can be traced from the right hand end of secondary 44 through conductor 56, flame relay 57, conductor 58, second stage 41, conductor 48, conductor 51, timer switch C2, and conductor 49 to the left hand end of secondary 44.

The current conducting path, traced above, shows'that the timer switch C2 must be closed to operatively connect the second stage 41 to the secondary 44.

At first glance it would seem that the second stage 41 of the electronic flame detector 19 is rendered inoperative when timer switch C2 opens after approximately two seconds of operation of the timer 18 to disconnect this stage from secondary 44. However, if it is assumed for the moment that the main relay 17 is energized, a circuit can be traced which shunts switch C2. This circuit maintains the second stage 41 operatively connected to secondary 44 after timer switch C2 opens and can be traced from the right hand end of secondary 44 through conductor 56, flame relay 57, stage 41, conductor 48, movable switch blade 27 and contact 34 of relay 17, conductor 53, and conductor 49 to the left hand of secondary 44.

The flame relay 57 includes a winding 59 and movable switch blades 60, 61 and 62. The full line positions of switch blades 61) through 62 in Figure 1 is the deenergized position, which is the position the switch blades assume when the second stage 41 of the electronic flame detector 19 is substantially non-conducting. The broken line position of switch blades 60 through 62 is the energized position of the switch blades and is the position the switch blades assume when the flame relay 57 is energized due to the second stage 41 being in a conducting state. With the relay 57 in a deenergized condition the movable switch blades 61 and 62 engage contacts and 63 respectively. When the flame relay 57 is energized the movable switch blades 60 and 62 engage the contacts 64 and 66 respectively, as shown by the dotted line position of the switch blades.

As pointed out above, when the apparatus of Figure l in the standby condition, the resistor 47 is short circuited by movable switch blade 27 and contact 32 of control relay 17 and therefore the second stage 41 of the electronic flame detector 19 is rendered conductive to energize the flame relay 57. This means that the movable switch blades 60, 61, and 62 of flame relay 57 are in the energized or broken line position shown in Figure 1.

As an additional safety feature the energizing circuit for the main control relay 17 includes a safety cutout device 67 having a heater 68, a bi-metal actuator 69, normally closed contacts and 71, and a reset actuator 72. The safety cutout device 67 operates upon a predetermined timed period of energization of heater 68 to cause the bi-metal actuator 69 to warp to the left out from under the normally closed contacts 70 and 71. These contacts then open to break the energizing circuit for the main control relay 17. Upon cooling of the bi-metal actuator 69 the reset actuator 72 is depressed manually to reset the contacts 70 and 71 to their normally engaged position as shown in Figure 1.

Operation To completely explain the operation of the program burner control apparatus of Figure 1 it is necessary to first assume that power is supplied to the power supply lines 20 and 21 but that the master switch 22 is in the open circuit position so that no power can be supplied to the apparatus. Therefore, the main control relay 17 and the flame relay 57 are deenergized. It will further be assumed that the timer motor 18 is in the start position so that the switches C1 through C10 are as shown in Figure 1, namely switches C1, C2 and C9 are in circuit closing position while switches C3, C4, C5, C6, C7, C8 and C10 are in circuit opening position.

Assume now that the master switch 22 is closed. The only immediate effect that this has upon the apparatus is to energize the transformer 42 associated with the electronic flame detector 19. This energizing circuit can be traced from power line conductor 21 through master switch 22, conductor 73, conductor 74, conductor 75, conductor 76, conductor 78, primary 43 of transformer 42, and conductor 79 to power line conductor 20. En ergization of transformer 42 energizes the filament winding 45 associated with the electronic flame detector 19 and energizes the high voltage secondaries 44 and 200 associated with the flame detector. A short time thereafter the electron discharge devices of the electronic flame detector are heated and are capable of conducting current.

Since no flame is present at the burner unit 10 the photo electric cell 16 detects the absence of flame and, as described in the above mentioned patent to Richard S. Fiegal, the first stage of the electronic flame detector is rendered conductive. It will be remembered that the conducting current of the first stage 40 normally flows through the resistor 47 to bias the second stage 41 to be non-conductive upon the absence of flame at the burner unit 10. However, at this time the main control relay 17 is in the deenergized condition and movable switch blade 27 and contact 32 short this resistor 47 in the manner above mentioned. Therefore, the second stage 41 of the electronic flame detector is also in a conducting state as soon as the filament of the associated electron discharge device is heated to operating temperature. The net effect is that flame relay 57 is allowed to move to the energized position when in fact no flame is present at the burner unit .11). Energization of the flame relay 57 causes the movable switch blades 60, 61, and 62 to move from the full line position shown in Figure 1 to the dotted line position. In the dotted line position of Figure l the switch blades 6% and 62 engage contacts 64 and 66 respectively. The movable switch blades 65 61, and 62 in moving to the energized position do not perform a useful switching function at this time.

This is the standby condition of the burner control apparatus of Figure 1 and is the condition in which the master switch 22 is in the circuit closing position, relay 17 is deenergized, timer motor 18 is deenergized and is in the start position, and flame relay 57 is in the energized position. Assume now that start button is depressed to indicate the need for operation of the burner unit 10.

Depressing the start button 25 completes an energizing circuit to a transformer 86 having a primary 81 and a tapped secondary 82. This energizing circuit can be traced from power line conductor 21 through master switch 22, conductor 73, limit switch 23, stop button 24, start button 25, conductor 83, and primary 81 of transformer 31 to power line conductor 20. As soon as transformer 81?: is energized the main control relay 17 moves to the energized position. An energizing circuit for the relay 17 can be traced from the right hand terminal of secondary 32 through winding 26 of relay 17, conductor 33, normally engaged contacts 71 and 70 of safety cutout device 67, conductor 84, conductor 85, timer switch C1, conductor 86, contact 66 and movable switch blade 62 of flame relay 57, conductor 117, conductor 94, switch C9, conductor 93, conductor 92, and heater 68 of safety cutout device 67 to the left hand terminal of secondary 82.

With the energization of main control relay 17, the movable switch blades 27 and 31 disengage contacts 32 and 33 and move into engagement with contacts 34 and 38 while the movable switch blades 28, 29, and move into engagement with contacts 35, 36, and 37 respectively.

This completes a shunt circuit about the start button 25 allowing the start button to be released to assume its open circuit position as shown in Figure 1. This shunt circuit can be shown by tracing a circuit from the lower terminal of the start button through conductor 97, conductor 98, conductor 99, contact 37 and movable switch blade 30 of relay 17, conductor 111i and conductor 161 back to the upper terminal of the start button 25.

Energization of relay 17 also causes movable switch blade 31 to disengage contact 33 and to move into engagement with contact 38. The disengaging of contact 33 performs no useful function at this time. However, the engaging of contact 38 by movable switch blade 31 completes an energizing circuit for the timer motor 18 as soon as flame relay 57 returns to the deenergized position, as will be shown.

As soon as movable switch blade 27 of relay 17 disengages contact 32, the shunt circuit around resistor 47 of electronic flame detector 19 is removed and the second stage &1 of the flame detector is rendered non-conductive in response to the photoelectric cell 16 detecting the absence of flame at the burner unit It). With the second stage of the electronic flame detector rendered non-conductive the flame relay 57 returns to the deenergized position, the movable switch blades 69, 61, and 62 of the flame relay moving to the full line position shown in Figure 1.

It will be remembered that the initial energizing circuit for control relay 17 included the movable switch blade 62 engaging contact 66 of the flame relay 57. This circuit is now broken, however, with the energization of relay 17 the movable switch blade 28 engages contact 35 and establishes a holding energization circuit for the control relay 17. This holding energization circuit can be traced from the right hand terminal of secondary 82 through winding 26 of relay 17, conductor 63, normally engaged contacts 71 and '71 of safety cutout device 67, conductor 84, conductor 85, timer switch C1, conductor 90, movable switch blade 28 and contact 35 of relay 17, and conductor 91 to the tap of secondary 82.

From the above traced circuits it can be seen that both the initial energizing circuit and this holding circuit for the relay 17 depend upon the timer motor 18 being in the start position to close the timer switch C1.

A further holding circuit is established for relay 17 when this relay is energized and can be traced from the right hand terminal of secondary 82 through winding 26, conductor 83, normally engaged contacts 71 and of safety cutout device 67, conductor 84, conductor 96, contact 36 and movable switch blade 29 of relay 17, conductor 95, conductor 94, timer switch C9, conductor 93, conductor 92, and heater 68 of safety cutout device 67 to the left hand terminal of secondary 82. This holding circuit is independent of timer switch C1. However, it does include the heater 68 of safety cutout device 67 and timer switch C9. Timer switch C9 is shunted by movable switch blade 62 engaging contact 63 of flame relay 57 and therefore this circuit will remain energized after timer switch C9 opens at approximately 52 seconds if flame relay 57 is not energized in the meantime. The effect of energization of flame relay 57 before the 5 2 second point is reached will be discussed later.

As above mentioned, energization of the relay 17 causes the movable switch blade 27 to disengage contact 32 and to engage contact 34. The disengagement of switch blade 27 with contact 32 renders the electronic flame detector 19 operative to detect the presence or absence of flame at the burner unit 13 due to the fact that resistor 47 is no longer shorted. The engaging of switch blade 27 with contact 34 places a shunt circuit about the timer switch C2. Switch blade 27 in this position functions to hold the second stage 41 of the electronic flame detector operatively connected to the power source at secondary 44 after the timer motor has moved from the start position and has operated approximately two seconds to open the timer switch C2.

The flame detector 19, as above mentioned, causes flame relay 57 to return to the deenergized position when the short about resistor 47 is removed. When movable switch blade 61 of flame relay 57 engages contact 65, the above mentioned initial energizing circuit for timer motor 18 is completed and can be traced from power line conductor 21 through master switch 22, conductor 73, conductor 74, conductor 75, conductor 76, conductor 102, movable switch blade 61 and contact 65 of flame relay 57, conductor 1113, contact 38 and movable switch blade 31 of relay 17, conductor 104, timer motor 18, and conductor to power line conductor 20. The timer motor 18 now starts to operate and to control the timer switches C1 through C10 in the sequence shown in Figure 2.

The burner control apparatus of Figure 1 is now in what may be called the starting phase of its operation. The main burner control relay 17 is energized, the heater 63 of the safety cutout device 67 is energized, the electronic flame detector 19 is detecting the absence of flame at the burner unit 10 to hold the flame relay 57 in a deenergized condition and the timer motor 18 is operating.

The operation of flame detector 19 up to this time has been such that it must be capable both of detecting the absence of flame and of detecting the presence of flame before timer motor 18 can be energized. In the standby condition flame is simulated by control relay 17 being in the deenergized position. In order for control relay 17 to move to the energized position upon a need for opera- 7 tion of the burner unit 10, the flame relay 57 must be in the energized position, or in other words, the flame detector 19 must respond to the simulation of flame to energize relay 57. Once control relay 17 moves to the energized position flame is no longer simulated in flame detector 19 and flame relay 57 becomes deenergized. In this way the ability of flame detector 19 to detect the absence of flame is checked. With flame relay 57 deenergized and control relay 17 energized a circuit is established to energize timer motor 18 and subsequently energize burner unit 10. Therefore it can be seen that before burner unit can be energized the ability of the flame detector 19 to detect the presence and the absence of flame is checked.

After the timer motor 18 has operated for approximately two seconds the timer switches C3, C4, C8 and C10 are moved to the closed position. The closing of timer switch C3 performs no useful function at this time. The function of switches C3 and C10 will be discussed later in the operation of the apparatus.

The closing of switch C4 completes an energizing circuit for the blower motor 11 through a manual switch 106. This energizing circuit can be traced from power line conductor 21 through master switch 22, conductor 73, conductor 74, conductor 107, timer switch C4, conductor 108, manual switch 106, conductor 109, blower motor 11, and conductor 110 to power line conductor 20. It will be noted that in Figure l the manual switch 106 is at the post purge position. This provides for energization of the blower motor 11 after the stop button 24 has been depressed at the end of a call for operation of the burner unit 10. If this manual switch 106 were set at the no post purge position the blower motor 11 is energized as soon as the start button 25 is depressed and is deenergized as soon as the stop button 24 is depressed.

The closing of timer switch C8 connects flame rod 116 in parallel with photocell 16 so that the flame detector 19 may detect pilot flame when pilot valve and ignition transformer 14 are energized.

After approximately three seconds of operation of the timer motor 18 the timer switches C1 and C2 are moved to the open circuit position. The opening of switch C2 opens the circuit which initially operatively connects the second stage 41 of the electronic flame detector 19 to the secondary 44; however, it will be remembered that the switch C2 is shunted by movable switch blade 27 and contact 34 of relay 17 to hold the second stage of the electronic flame detector operatively connected to secondary 44.

Opening of the timer switch C1 breaks the above mentioned initial energizing and holding circuit for the relay 17. However, the relay 17 is maintained energized through the further holding circuit above traced, which circuit is independent of timer switch C1.

After approximately six seconds of operation of the timer motor 18 the timer switch C5 moves to the circuit closing position. The closing of switch C5 completes a holding circuit for timer motor 18 which is independent of whether or not the main burner relay 17 or the flame relay 57 are energized or deenergized. This holding circuit can be traced from power line conductor 21 through master switch 22, conductor 73, conductor '74, conductor 75, conductor 111, timer switch C5, conductor 112, timer motor 18, and conductor 105 to power line conductor .20. From this above traced circuit it can be seen that the timer motor 18 will remain energized until switch C5 opens, which upon reference to Figure 2 can be seen to occur at approximately 96 seconds. This continued energization of the timer motor 18 is dependent only upon continued application of power to the power lines 20 and 21 and upon continued closure of the master switch 22.

At this time it is Well to consider the manner in which the apparatus of Figure l is now operating. Upon reference to Figure 2 it is apparent that the timer switches C1, C2, C6, C7 and C8 are in the open position while the timer switches C3, C4, C5, C9 and C10 are in the circuit closing position. It will also be remembered that the main control relay 17 is maintained energized through only the further holding circuit and this circuit includes both movable switch blade 28 and movable switch blade 29 of relay 17 in the energized position. Likewise, the second stage 41 of the electronic flame detector 19 is op eratively connected to the left side of the secondary 44 through the switch blade 27 of the relay 17 in the energized position. It will now be assumed for the purpose of explanation that a power failure occurs at this time, namely after the timer motor has run for a total time of somewhat greater than six seconds. Upon such a power failure it is clearly evident that the relays 17 and 57 will move to the deenergized position and that the electronic flame detector 19 will become deenergized. It is also apparent that the timer motor 18 will be deenergized and will stop operation of its switches.

Upon the reapplication of power to the power line conductors 20 and 21 the timer motor 18 will again be energized since the holding circuit for the timing motor 18 is independent of the condition of the relays 1'7 and 57. However, the main burner control relay 17 cannot move to energized position since the initial energizing circuit for this relay is broken at the now open timer switch C1 and the holding circuits for relay 17 are broken since the movable switch blades associated with relay 17 are in their deenergized positions. Therefore, the relay 17 can appropriately be called a power failure relay since it is responsive to the interruption of power to prevent reenergization of itself. Another important feature of the present invention is that after a momentary power failure the second stage of the electronic flame detector 19 is maintained disconnected from the secondary 44 and it is impossible under any condition for the flare relay 57 to move to the energized position after such a power failure. This important feature of the present invention will be discussed later in the explanation of the improved program burner control apparatus.

Going back once again to the normal operation of the apparatus of Figure 1, after approximately 33 seconds of operation of the timer motor, the timer switch C6 is moved to the circuit closing position. witch C6 in the circuit closing position completes an energizing circuit for the pilot valve 15 and the ignition transformer 14. This energizing circuit can be traced from power line conductor 21 through master switch 22, conductor 73, limit switch 23, stop button 24, conductor 101, conductor 100, movable switch blade 30 and contact 37 of relay 17, conductor 99, conductor 113, timer switch C6, conductor 114, pilot valve 15 and ignition transformer 14 connected in parallel, and conductor to power line 20. Fuel will now pass through the pilot valve 15 and will be ignited by the ignition spark produced upon energization of the ignition transformer 14. Since the flame rod 116 is connected through timer switch C8 to the electronic flame detector 19, the flame relay 57 will now move to the energized position in response to the establishment of pilot flame.

Energization of the flame relay 57 causes movable switch blades 60, 61 and 62. to move to the energized or broken line position shown in Figure 1. Movable switch blade 60 in engaging contact 64 completes a portion of a circuit for the main fuel valve 12, however, the complete energizing circuit for the main fuel valve 12 is still open so that movable switch blade 60 engaging contact 64 has no effect at this time.

Upon energization of flame relay 57 movable switch blade 61 disengages contact 65 and this breaks the initial energizing circuit for the timer motor 18. However, it will be remembered that the timer motor 18 is held energized through the holding circuit which includes timer switch C5. Therefore, the movement of movable switch blade 61 to the energized position has no effect at this time. 7

Movable switch blade 62 of relay 57 also moves to the energized position and moves from a position of engagement with contact 63 to a position of engagement with contact 66. The disengagement of switch blade 62 with contact 63 opens the circuit shunting timer switch C9. However, switch C9 is closed at this time and opening this shunt circuit has no effect.

The engagement of switch blade 62 with contact 66 establishes still another holding circuit for main control relay 17 and also establishes another energizing circuit for heater 68 of safety cutout device 67. It will be remembered that just before flame was detected by flame detector 19, relay 17 was energized through the above traced further holding circuit which includes timer switch C9 and heater 68 of safety cutout device 67. Energization of flame relay 57 in response to the establishment of pilot flame does not open this further holding circuit but does complete still another holding circuit for relay 17. This circuit can be seen by tracing a circuit from the right hand terminal of secondary 82 through winding 26 of relay 17, conductor 83, normally engaged contacts 71 and 70 of safety cutout device 67, conductor 84, conductor 96, contact 36 and switch blade 29 of relay 17, conductor 95, conductor 117, switch blade 62 and contact 66 of flame relay 57, conductor 86, conductor 90, switch blade 28 and contact 35 of relay 17, and conductor 91 to the tap of secondary 82. From this last traced circuit it can be seen that relay 17 is now energized independent of timer switch C9 and independent of heater 68 of safety cutout device 67. However, relay 17 is still functioning as a power failure relay since it is energized through switch blades 28 and 29 of relay 17.

Heater 68 of safety cutout device 67 is still energized at this time through the further holding circuit for relay 17. However, upon engagement of switch blade 62 with contact 66 of flame relay 57 another energizing circuit for heater 68 can be traced from the left hand terminal of secondary 82 through heater 68, conductor 92, conductor 93, switch C9, conductor 94, conductor 117, switch blade 62 and contact 66 of flame relay 57, conductor 86, conductor 90, switch blade 28 and contact 35 of relay 17, and conductor 91 to the tap of secondary 82. Therefore, heater 68 remains energized even though pilot flame has been established. However, after timer motor 18 has run for a total time of 52 seconds switch C9 will open to open both the further holding circuit relay 17 which included heated 68 and to open the last traced circuit for heater 68, thereby deenergizing heater 68.

Safety cutout device 67 may have a variety of timings, the only requirement being that the device not be timed to operate before switch C9 opens. For example, with safety cutout device 67 being timed to open contacts 70 and 71 after 60 seconds of energization of heater 68 the heater is energized for 52 seconds at the time switch C9 opens. If flame has been established at this time the heater is deenergized. However, if flame has not been established the heater is maintained energized through switch blade 62 and contact 63 which shunt switch C9 and in 8 additional seconds contacts 70 and 71 of safety cutout device 67 open to deenergize main control relay 17.

At this point in the description of the apparatus of Figure 1 it is well to explain the function of timer switch C10. The closing of timer switch C18 completes a circuit which bridges from switch blade 61 of flame relay 57 to the contact 65. Therefore timer switch C10 holds timer motor 18 energized and becomes a part of the above traced initial energizing circuit to hold timer motor 18 energized independent of switch blade 61 and contact 65 of relay 57. At first glance, the timer switch C10 may appear to be an extra switch performing no function since at this time the fuel valves 12 and 15 of the burner unit 10 are deenergized and therefore the need for shunting the switch blade 61 and contact 65 of flame relay 57 is not apparent. However, it is possible that the operator of the control apparatus of Figure 1 may wish to advance the time at which the pilot valve 15 and ignition transformer 14 are energized. This can be done by altering the particular cam, not shown, associated with timer switch C6 so that the valve and transformer are energized soon after timer motor 18 starts to run. In this case pilot flame will be established before timer switch C5 closes the holding circuit for the timer motor 18. If it were not for timer switch C10 this would cause the timer motor to be deenergized as the electronic flame detector 19 detected the pilot flame and opened the above mentioned initial energizing circuit for timer motor 18. In this instance timer switch C10 functions to hold the timer motor 18 energized until timer switch C5 closes. Timer switch C10 can be set to open at any time after timer switch C5 closes but must be set to open before timer switch C5 opens, for example, at the 60 second point.

After approximately 39 seconds of operation of the timer motor 18 the switch C7 closes. This completes the energizing circuit through the movable switch blade 60 of the flame relay 57 to the main burner valve 12. This circuit can be traced from power line conductor 21 through master switch 22, conductor 73, limit switch 23, stop button 24, conductor 101, conductor 118, timer switch C7, conductor 119, contact 64 and movable switch blade 60 of flame relay 57, conductor 120, main fuel valve 12, and conductor to the power line conductor 20. With the main fuel valve 12 now energized and with pilot flame present the main burner will be ignited.

After the timer motor 18 has operated for approximately 47 seconds the switch C8 opens. It will be remembered that this switch C8 connects the flame rod 116 to the electronic flame detector 19. The opening of this circuit renders continued energization of the flame relay 57 by the electronic flame detector 19 conditioned upon the photocell 16 detecting the main burner flame. In this manner a check is made to insure that the main burner is ignited by the pilot flame. The normal operation of the burner unit 10 is such that the main burner flame is established upon main burner valve 12 being energized.

The timer motor 18 continues to operate until after approximately 52 seconds switch C9 opens. Switch C9 breaks the before traced energizing circuits for the heater 68 of the safety cutout device 67. These circuits are broken at this time since the electronic flame detector 19 has detected flame at the burner unit 10 and the movable switch blade 62 of relay 57 is disengaged from contact 63. It will be remembered that with the movable switch blade 62 engaging contact 63 a shunt circuit is completed around switch C9 and if it were not for the fact that flame had been detected at the burner unit 10 to open this shunt circuit the heater 68 of safety cutout device 67 would remain energized at this time.

After approximately 59 seconds of operation of the timer motor 18, switch C6 opens. This switch is in the energizing circuit for the pilot valve 15 and ignition transformer 14. Therefore, the pilot valve and ignition transformer are now deenergized.

After the timer motor 18 has run for a total time period of approximately 96 seconds, switch C5 opens. This switch is in the holding circuit for the timer motor 18 and opens the holding circuit. The flame relay 57 is energized at this time to open the initial energizing circuit for timer motor 18. Therefore, the timer motor stops.

This is the run position of the apparatus of Figure 1, with relay 17 energized, timer motor 18 deenergized, flame relay 57 energized in response to the presence of fiame at the burner unit 10, and with the timer switches C1, C2, C5, C6, C8, and C9 open. The timer switch C3 is closed and is in a circuit which is conditioned to again energize the timer motor 18 upon the relay 17 becoming deenergized in response to the stop button 24 being depressed. This circuit will be described more completely later in this description. The timer switch C4 is closed C3 opens.

and it will be remembered that this switch controls energization of the burner motor 11 so long as the manual switch 106 is at the post purge position. Switch C7 is also closed at this time and this switch inconjunction with switch blade 60 and contact 64 of flame relay 57 controls the energizing circuit of the main fuel valve 12.

Operation of the apparatus of Figure 1 will continue in this manner until it is desired to discontinue operation of the burner unit 10. The stop button 24 is then depressed.

'The energizing circuit for transformer 80 includes at all times the stop button 24 and therefore the main control relay 17 will become deenergized in response to actuation of the stop button 24. This immediately causes the movable switch blades 27 through 31 of relay 17 to move to the deenergized position.

In the deenergized position of relay 17, the movable switch blades 28 and 29 disengage the contacts 35 and 36 respectively. These switch blades being in the holding circuit for relay 17 prevent the reenergization of the relay 17 if the start button is immediately depressed, it being remembered that the initial energizing circuit for relay 17 is broken at the timer switch C1 which is now open. Movable switch blade of relay 17 also disengages contact 37. This switch blade and contact are in the energizing circuit for the pilot valve 15 and ignition transformer 14, however, this circuit is already open at timer switch C6. If the manual switch 106 were at the no post purge position the blower motor 11 would also be deenergized at this time. In the apparatus of Figure l the manual switch 106 is shown at the post purge position and therefore the blower motor 11 is controlled only by the timer switch C4 which is closed at this time to keep the blower motor energized.

Deenergization of relay 17 also causes movable switch blade 27 to disengage contact 34 and to engage contact 32. It will be remembered from the above traced circuits that the second stage 41 of the electronic flame de tector 19 is operatively connected to the left hand end of secondary 44 through movable switch blade 27 and contact 34 of relay 17 so long as the timer switch C2 is open, as it is at this time. Therefore, when movable switch blade 27 disengages contact 34 the second stage 41 of electronic flame detector 19 is disconnected from secondary 44 and power is removed from this stage so that the flame relay 57 becomes deenergized. Considering now the engagement of movable switch blade 27 with contact 32, it will be remembered that this shorts resistor 47 and simulates the presence of flame in the flame detector 19 to normally cause the second stage 41 of the flame detector to energize the flame relay 57. However, i

at this time this second stage 41 is not connected to the source of power, secondary 44, and the flame relay 57 therefore cannot move to the energized position.

The last function accomplished by deenergization of relay 17 is that movable switch blade 31 disengages contact 38 and engages contact 33. Movable switch blade 31 in engagement with contact 38 formed a portion of the initial energizing circuit for timer motor 18 which during the run position was open circuited at movable switch blade 61 and contact 65 of flame relay 57. When movable switch blade 31 moves into engagement with contact 33 a further energizing circuit is established for the timer motor 18 which causes the timer motor 18 to run for an additional 15 seconds from the 96 second position of Figure 2 to the 111 second or start position of Figure 2. This energizing circuit for the timer motor 18 can be traced from power line conductor 21 through master switch 22, conductor 73, conductor 74, conductor 107, timer switch C3, conductor 130, contact 33 and movable switch blade 31 of relay 17, conductor 104, timer motor 18, and conductor 105 to power line conductor 20. This circuit cannot be broken until timer motor 18 returns to the start position at which time the timer switch From the above traced circuit it can be seen that this further energizing circuit for timer motor 18 also includes the movable switch blade 31 and contact 33 of relay 17. However, due to the fact that the initial energizing circuit for this relay is open circuited at timer switch C1 it is impossible for this relay to become energized to break this further energizing circuit for the timer motor 18.

When timer motor 18 arrives at the start position switch C4 is opened. With the manual switch 106 in the post purge position the blower motor 11 is energized under control of this timer switch C4 and the opening of this switch when the timer motor 18 returns to the start position deenergizes the burner motor 11.

With the timer motor 18 in the start position it can be seen from Figure 2 that the timer switches C1, C2 and C9 are again closed while the other timer switches are open. Closing of the timer switch C1 completes the initial energizing circuit for the main control relay 17 so that this relay will move to the energized position as soon as the primary 81 of transformer is energized in response to the start button 25 being depressed. Closing of the timer switch C9 conditions a holding circuit for the main control relay 17 to be completed when the movable switch blade 29 of relay 17 engages contact 36.

The closing of timer switch C2 completes a circuit which renders the second stage 41 of the electronic flame detector 19 operative. With the resistor 47 of flame detector 19 now short circuited by movable switch blade 27 and contact 32 of relay 17 and with power supplied to the second stage 41 of the flame detector, a flame is simulated in the flame detector 19 and the flame relay 57 moves to the energized position.

This is the standby condition of the apparatus of Figure 1 wherein the main control relay 17 is deenergized, the timer motor 18 is deenergized in the start position, and the electronic flame detector 19 is responding to a simulated flame to energize the flame relay 57. The apparatus will stand in this position until there is another call for operation of the burner unit 10 as evidenced by actuation of the start button 25.

Actuation of the start button 25 will cause the apparatus of Fi ure l to repeat the cycle of operation as outlined above. If it is assumed that due to a defect in the burner unit 10 flame is not established either at the pilot or the main burner it will be recognized that once the flame relay 57 is returned to the deenergized position in response to the main control relay 17 being energized it will remain in this position as an indication of the absence of flame at the burner unit 10. Therefore, when the timer motor 18 comes to the point where it has run for a total of approximately 52 seconds, at which time it opens the switch C9, the energizing circuit for the heater 68 of the safety cutout device 67 will not be opened. This can be seen more clearly by tracing an energizing circuit from the right hand terminal of secondary 82 through winding 26 of relay 17, conductor 83, normally engaged contacts 71 and 70 of safety cutout device 67, conductor 84, conductor 96, contact 36 and the movable switch blade 29 of relay 17, conductor 95, conductor 117, movable switch blade 62 and contact 63 of flame relay 57, conductor 87, conductor 92, and heater 68 of safety cutout device 67 to the left hand terminal secondary 82. A short period of time after opening of switch C9 the safety cutout device 67 will be actuated to open the normally engaged contacts 70 and 71. For eXample, the safety cutout device 67 may have a 60 second timing so that approximately 8 seconds after the timer switch C9 opens the safety cutout device actuates the contacts 70 and 71 to the open circuit position. This causes deenergization of the main control relay 17 and its movable switch blades assume their deenergized position as shown in Figure l.

The timer motor 18 is at this time energized by means of the holding circuit which includes only the timer switch C and therefore the timer motor 18 continues to operate. Deenergization of the main control relay 17 however, causes the resistor 47 of electronic flame detector 19 to be short circuited and therefore a flame is simulated. However, with the timer motor 18 moved away from the start position to open the timer switch C2 and with the main control relay 17 in the deenergized position to break the engagement of movable switch blade 27 with contact 34 the second stage 41 of the electronic flame detector is disconnected from the secondary 44 of the transformer 42. Therefore, the flame relay 57, which at this time is considered to be deenergized is positively insured from assuming the energized position.

The timer motor 18 continues to run. However, actuation of its switches does not energize the burner unit since both the main control relay 17 and the flame relay 57'are in the deenergized position. Considering now the time 96 seconds after the timer motor 18 first began to operate, the switch C5 will open to break the holding circuit for the timer motor 18. This is the normal run position of the apparatus and normally if flame had been established at the burner unit 11 the timer motor 18 would stop in this position until the stop button 24 was depressed to indicate that there was no longer a need for operation of the burner unit 10. However, since flame has not been established at the burner unit 10 and since this has caused the safety cutout device 27 to open the normally engaged contacts 70 and 71 to deenergize relay 17, the above mentioned further energizing circuit for the timer motor 13 is now completed through the timer switch C3 and through the movable switch blade 31 and contact 33 of relay 17. The timer motor 18 will now run for an additional 15 seconds and return the apparatus to the start position from which position the apparatus may recycle upon the start actuator again be depressed.

Now assume that the start actuator 25 has again been depressed, that the control apparatus controls the burner unit 1t in the normal sequence to reach the run position wherein the main control relay 17 is energized, that the timer motor 18 is deenergized, and that the flame relay 57 is energized and detecting the presence of flame at the burner unit 10. It is possible that during the run period of the burner unit 11) the burner unit will develop a faulty condition such as contamination of the fuel so that flame is extinguished at the burner unit. This absence of flame is detected by the flame detector 19 and flame relay 57 moves to its deenergized position. This immediately deenergizes the main fuel valve 12 to prevent the further feeding of fuel to the burner unit 10. This also opens the energizing circuit for relay 17. Since timer switch C9 is open at this time the operation of movable switch blade 62 between contacts 66 and 63 causes the main control relay 17 to be deenergized.

Deenergization of relay 17 causes the timer motor 18 to again be energized through the further energizing circuit which includes timer switch C3 and switch blade 31 of relay 17 in engagement with contact 33. To make this more clear this circuit can again be traced from power line conductor 21 through master switch 22, conductor 73, timer switch C3 conductor 130, contact 33, and movable switch blade 31 of relay 17, conductor 104, timer motor 18, and conductor 105 to power line conductor 20. Therefore, the timer motor 18 will again begin to operate and to cycle its associated switches in the manner shown in Figure 2 back to the start position from where recycle may occur upon actuation of start button 25.

In a burner control apparatus it is not only important to protect against flame failure but it is also important to provide safe operation of the burner unit being controlled if a momentary power failure occurs during any portion of the cycle of operation of the apparatus. It will be remembered that after approximately two seconds of operation of the timer motor 18 the switch C1 opens and the main control relay 17 can then be considered as a power failure relay. A power failure during the first two seconds 14 of operation of the timer motor 18 will not affect the ap-' paratus and upon the restoration of power the apparatus will again start up the cycle of operation from where it left off, provided the start button 25 is still in the depressed position.

It will be remembered that after approximately two seconds of operation of the timer motor 18 the continued connection of the second stage 41 of the electronic flame detector 19 to the center tap of secondary 14 is dependent upon energization of the main control relay 17. Therefore, if a momentary power failure occurs after the timer motor has operated for approximately two seconds and before the run position at 96 seconds is reached the main control relay 17 will become deenergized and the second stage 41 of the electronic flame detector will be disconnected from the power source, secondary 44, thereby causing the flame relay 57 to move to the deenergized position independent of whether or not photocell 16 or flame rod 116 is subjected to a flame at the burner unit 10. It will be remembered that the energizing circuit for the main valve 12 includes movable switch blade 69 of flame relay 57 in the energized position while the energizing circuit for pilot valve 15 includes movable switch blade 39 of relay 17. From this it can be seen that with relay 17 and relay 57 in the deenergized position no fuel can be supplied to the burner unit 10. The timer motor 18 will continue to operate by means of its holding circuit which includes the switch C5 until the 96 second run position is reached.

When timer motor 18 arrives at the 96 second position the holding circuit for the timer motor 18 is opened. However, the above mentioned further energizing circuit which includes timer switch C3 and movable switch blade 31 of main control relay 17 in the deenergized position is completed to cause the timer motor 18 to return to the start position. From this position the apparatus of Figure 1 may recycle upon the start button 25 again being depressed.

It is also possible that the apparatus of Figure 1 will arrive at the run position, the 96 second position of Figure 2, where the main control relay 17 and the flame relay 57 are energized and the timer motor 18 is deenergized, and then during the run period of the burner unit 10 that a momentary power failure will occur. Upon such a power failure both relay 17 and relay 57 will immediately assume their deenergized positions. Upon a resumption of power, relay 17 cannot again be energized due to the fact that its holding circuit which includes movable switch blades 28 and 29 of relay 17 is opened and its initial energizing circuit is open at timer switch C1. The flame relay 57 cannot be energized due to the fact that the second stage 41 of the electronic flame detector is disconnected from the secondary 44 due to the fact that movable switch blade 27 of relay 17 is in its deenergized position and also due to the fact that timer switch C2 is in open circuit position. However, the timer motor 18 is energized through the above mentioned further energizing circuit which includes timer switch C3 and movable switch blade 31 of relay 17 in the deenergized position. The timer motor 18 will then return to the start position from which position the apparatus of Figure 1 may recycle upon the start button 25 again being depressed.

A further safety feature which the apparatus of Figure 1 incorporates is that of component checking. While an electronic flame detector provides very fast sensing of the presence or absence of flame at a burner unit, this type of flame detector is also capable of faulty operation if the electronic discharge devices in the flame detector should fail or if other circuit components in the flame detector should fail. It is clear that any failure in the electronic flame detector which would cause the flame relay to always remain in the position indicative of the absence of flame would be a safe failure. However, the fault which must be protected against is the failure where the electronic flame detector causes the flame relay to be energized independent of whether or not a flame is in fact present at the burner unit being controlled.

In the apparatus of Figure 1, if such an unsafe failure has occurred during standby condition of the apparatus of Figure 1 the depressing of start button will cause main control relay 17 to be energized in the normal manner and this includes energization of the heater 68 of safety cutout device 67. Energization of relay 17 causes the shunt circuit about resistor 47 of electronic flame detector 19 to be removed and normally the flame relay 57 assumes its deenergized or no flame position. However, if an unsafe failure has occurred in the flame detector the flame relay 57 will remain in the energized position. With the flame relay 57 and the main control relay 17 in the energized position, the initial energizing circuit for the timer motor 18 cannot be completed and the apparatus of Figure 1 will stand in this condition with both relays 57 and 17 energized and with timer motor 18 deenergized until the safety cutout device 67 is actuated to open the normally engaged contacts 70 and 71 at which time the main control relay 17 will become deenergized.

It is also possible that the apparatus of Figure 1, upon actuation of start button 25, will operate for a prolonged period of time due to the operator of the installation failing to actuate stop button 24. 23 will prevent possible damage to the installation due to such prolonged operation of burner unit 10. Figure 1 shows that limit switch 23 is connected in series with stop button 24. Therefore, when limit switch 23 moves to the circuit opening position the effect is the same as if stop button 24 had been depressed. This deenergizes burner unit 10 to prevent its continued operation and also deenergizes transformer 80 thereby causing main control relay 17 to assume its deenergized position. Timer motor 18 is now energized through the energizing circuit which includes timer switch C3 and switch blade 31 of relay 17 engaging contact 33. The timer motor 18 therefore re turns to start position and the apparatus of Figure 1 assumes its standby condition once again.

The above explanation of the apparatus of the present invention has been restricted for purposes of explanation to a particular sequence of operation of the timer motor switches C1 through C9. While a conventional sequence of operation of the burner unit has been selected for the explanation of the present invention it is to be understood that the invention is not to be limited to the particular sequence of operaion of the burner unit which has been described.

It can be seen from the above explanation that we have provided an improved program burner control apparatus wherein a main control means, a flame detector, and a timer have been so interconnected that extremely safe operation of the burner unit is accomplished.

We claim as our invention:

1. A program type burner control for use with a fuel burner comprising: an electrically energizable timer having an actuator and a plurality of switches controlled thereby in a predetermined sequence of operation from a start position; an electrically energizable flame detector, a flame relay including an actuator controlled by said flame detector and switching means operated by said actuator, said flame relay having an energized position indicative of the presence of flame and a deenergized position indica tive of the absence of flame; a burner control relay having an actuator and switching means controlled thereby, said burner control relay having an energized position indicative of the need for operation of the fuel burner and a deenergized position indicative of no need for operation of the fuel burner; first circuit means controlled by said burner control relay switching means in said deenergized position connecting said flame detector to simulate the presence of flame and cause said flame relay to move to said energized position; second circuit means controlled by said flame relay switching means in said energized position and by a first of said switches of said timer in In this case limit switch start position adapted to energize said burner control relay actuator upon a need for operation of the fuel burner, said burner control relay being energized upon such need to discontinue the simulation of flame in said flame detector, said flame detector thereafter detecting the absence of flame to cause said flame relay to move to said deenergized position; third circuit means including said flame relay switching means in said deenergized position and said burner control relay switching means in said energized position to energize said timer actuator; and fourth circuit means controlled by said burner control relay switching means in said energized position to maintain said burner control relay actuator energized independent of said first switch of said timer as long as there is a continued need for operation of the fuel burner.

2. A program type burner control for use with a fuel burner comprising: an electrically energizable timer motor and a plurality of cam operated switches controlled thereby in a predetermined sequence from a starting position upon energization of said timer motor, a first and a second of said switches being closed in starting position and opened after a short period of operation of said timer motor; an electrically energizable flame detector, a flame relay including an operator connected to said flame detector and switching means controlled thereby, said flame relay moving to an energized position upon the presence of flame and to a deenergized position upon the absence of flame; an electrically energizable control relay having an operator and switching means controlled thereby, said control relay moving to an energized position upon the need for operation of the fuel burner and to a deenergized position upon no need for operation of the fuel burner; first circuit means controlled by the switching means of said control relay in deenergized position to simulate the presence of flame in said flame detector so that said flame relay moves to said energized position; second circuit means controlled by said switching means of said flame relay in energized position, switch means responsive to the need for operation of the fuel burner, and said first of said switches controlled by said timer motor to energize said control relay to thereby cease the simulation of flame in said flame detector and allow said flame detector to sense the absence of flame to deenergize said flame relay; holding means for said control relay controlled by the switching means of said control relay to maintain said control relay energized independent of said second circuit means; third circuit means controlled by the switching means of said control relay in energized position and the switching means of said flame relay in deenergized position to energize said timer motor; fourth circuit means controlled by a third of the cam operated switches controlled by said timer motor to energize the fuel burner a period of time after the opening of said first and second switches controlled by said timer motor; and means controlled by said second of said cam operated switches controlled by said timer motor to render the flame detector operative as long as said second switch is closed, said second switch being shunted by the switching means of said control relay in energized position, said shunting circuit being broken if a power failure occurs after said first cam operated switch opens said second circuit.

3. A program type burner control apparatus for use with a burner unit having a pilot burner and a main burner comprising; a timer having an electrically energizable actuator and a plurality of switches controlled thereby in a predetermined sequence from starting position upon energization of said timer actuator, a first and a second of said switches being closed at the starting position of said timer and opened shortly thereafter, a third one of said plurality of switches being closed after operation of said timer has started; an electronic flame detector having a plurality of stages, a flame relay connected to one of said stages to be actuated to energized position upon the presence of flame and to deenergized position upon the absence of flame; means including said first switch of said timer to render said one stage operative, an electrically energizable control relay; means controlled by means responsive to need for operating the burner unit to energize said control relay upon such a need and to deenergize said control relay upon no such need; means controlled by said control relay in deenergized position to connect said one stage of said flame detector to simulate the presence of flame and thereby cause said flame relay to be energized; means controlled by said flame relay in energized position, by means responsive to the need for operation of the burner unit, and by said second switch controlled by said timer to effect energization of said control relay; means controlled by said control relay in energized position completing a non-pickup holding circuit for said control relay which is independent of said second switch controlled by said timer, means controlled by said control relay in energized position also completing a shunt circuit around said first switch of said timer to thereby hold said one stage of said flame detector operative to respond to the presence or absence of flame after said first contact of said timer is opened by operation of said timer; means controlled by said control relay in energized position and said flame relay in deenergized position to effect energization of said timer actuator, circuit means controlled by said timer and adapted to be connected to the burner unit to establish flame at the pilot burner; and further circuit means adapted to be connected to energize the main burner and controlled by said third switch and by means controlled by said flame relay in energized position, said control relay functioning upon a momentary power failure to break said shunt circuit to thereby render said one stage of said flame detector inoperative so that said further circuit means cannot be completed after a momentary power failure.

4. Programing burner control apparatus for use with a burner unit and means responsive to the need for operation of the burner unit, comprising; an electronic flame detector having an output stage, a flame relay controlled by said output stage, a stage preceding said output stage, resistance means connecting in controlling relation to said output stage and connected in the current conducting path of said stage preceding said output stage, flame responsive means connected in controlling relation to said preceding stage, said preceding stage controlling the voltage across said resistance means to cause said flame relay to be deenergized upon the absence of flame, said voltage being reduced substantially to zero upon the presence of flame to cause said output stage to energize said flame relay; electrically energizable actuating means, a plurality of switches controlled by said electrically energizable means and actuated in a predetermined sequence upon energization of said electrically energizable means, circuit means controlled by a first switch of said electrically energizable means adapted to be connected to the burner unit, further circuit means controlled by a second switch of said electrically energizable means connecting said output stage of said electronic flame detector to a source of power, said last named circuit being closed when said switches controlled by said electrically energizable means are in starting position and opened a short period of time after said electrically energizable means is energized; electrically operable control means, switches controlled by said control means having an energized and a deenergized condition; a first of said control means switches in deenergized position shunting said resistance means to simulate flame and cause said flame relay to be energized by the output stage of said electronic flame detector; initial energizing circuit means for said control means including means controlled by said flame relay in energized condition and the means responsive to the need for operation of the fuel burner, said first of said control means switches in energized position opening the circuit shunting said resistance means to thereby allow said flame relay to become deenergized in response to the absence of flame,

holding circuit means for said control means controlled by a second switch of said control means in energized condition; circuit means controlled by a further switch of said control means to shunt said second switch of said electrically energizable means to maintain said output stage of said electronic flame detector connected to said source of power after said second switch opens; and circuit means controlled by said flame relay in deenergized condition and by a switch of said control means in energized condition adapted to energize said electrically energizable actuating means.

5. Program burner control apparatus for use with a fuel burner comprising; an electrically operable timer having a motor and a plurality of sequentially operated switches operated thereby, a control relay adapted to be controlled by means responsive to the need for operation of the fuel burner and movable from a first to a second position upon such a need, an electrically energizable flame detector, a flame relay controlled by said flame detector and movable from a first to a second position upon the presence of flame, circuit means controlied by one of said timer switches connecting said flame detector to a source of power, said one switch of said timer being closed when said timer is in start position and opened a short time period after said timer motor has been energized, circuit means controlled by said control relay in said first position to simulate a flame to cause said flame relay to move to said second position, circuit means controlled by a second of said switches of said timer and said flame relay in said second position to energize said control relay, said second switch being closed when said timer is in start position and opened a short time period after said timer motor has been energized, said control relay moving to said second position when energized, circuit means controlled by said control relay in said second position shunting said one timer switch and maintaining said flame detector connected to said source of power, further circuit means controlled by said control relay in said second position to hold said control relay energized independent of said second timer switch, means controlled by said flame relay in deenergized position and said control relay in energized position to energize said timer motor, and circuit means controlled by said timer to maintain said timer motor energized, said control relay responding to a momentary power failure to prevent reenergizing said control relay and to hold said flame detector disconnected from said source of power, said timer maintaining said motor energized until said timer returns to start position from which recycle can occur.

6. A program type burner control apparatus for use with a fuel burner comprising; a timer having an electrically operable actuator and a plurality of switches controlled thereby, circuit means controlled by certain of said switches adapted to energize the fuel burner upon energization of said timer actuator; an electrically energizable flame detector, switching means controlled by said flame detector and adapted to move from a first to a second position upon the detection of flame; power failure relay switching means adapted to move from a first to a second position upon a call for operation of the fuel burner, holding means for said power failure relay switching means completed by said power failure relay switching means in said second position to maintain said power failure relay switching means in said second position; a source of power; means controlled by a first of said switches of said timer momentarily closed at start position of said timer connecting said flame detector to said source of power; means controlled by said power failure relay switching means connecting said flame detector to said source of power when said power failure relay switching means is in said second position and connecting said flame detector to simulate the presence of flame when said power failure relay switching means is in said first position; means controlled by said switching means of said flame detector adapted to connect said power failure relay switching means to said source of power, said power failure relay switching means in said second position opening the connection simulating flame to allow said switching means of said flame detector to assume said first position in response to the absence of flame; and means controlled by said switching means of said flame detector in said first position and said power failure switching means in said second position adapted to connect said timer actuator to said source of power.

7. A program burner control apparatus for use with a fuel burner comprising; a power failure relay having an electrically operable actuator adapted to be energized upon a call for operation of the fuel burner, a timer having an actuator and a plurality of contacts controlled in a predetermined sequence from a start position upon energization of said timer actuator, circuit means including contacts of said timer adapted to be connected to energize the fuel burner upon said timer actuator being energized for a predetermined time period, an electrically energizable flame detector, a flame relay having an actuator connected to said flame detector to be energized upon the presence of flame, a source of power, circuit means controlled by contacts of said timer connecting said flame detector to said source of power when said timer is in start position and breaking the connection a short time period after said timer actuator is energized and caused to move from said start position, circuit means controlled by said power failure relay in deenergized position to simulate the presence of flame and cause said flame detector to energize said flame relay actuator, circuit means controlled by said power failure relay in energized position to connect said flame detector to said source of power, initial energizing circuit means adapted to energize said power failure relay actuator upon a call for operation of the fuel burner, said last named circuit means being opened by said timer after a short time period of energization of said timer actuator, holding circuit means for said power failure relay actuator controlled by said power failure relay in energized position, said power failure relay actuator being maintained energized by said holding circuit after said short time period of energization of said timer actuator only so long as there is no power interruption, initial energizing circuit means for said timer actuator completed by said flame relay in deenergized position and by said power failure relay in energized position, holding circuit means closed by contacts of said timer after a short time period of energization of said timer actuator to maintain said timer energized until said timer reaches a run position, and circuit means controlled by contacts of said timer and by said power failure relay in deenergized position to continue energization of said timer actuator to cause said timer to return to start position from which it may recycle if there has been a power failure during operation of said holding circuit means for said timer actuator.

8. A program burner control apparatus for use with a fuel burner comprising; a program timer having an electrically operable actuator and switch means controlled thereby, a power failure relay having an actuator controlled by means responsive to a call for operation of the fuel burner and having a switch means movable from a standby position to a second position upon a call for operation of the fuel burner, an electrically operable flame detector having switching means, a source of power, circuit means controlled by said program timer switch means in start position connecting said flame detector to said source of power, further circuit means controlled by the switch means of said power failure relay in said second position to hold said flame detector connected to said source of power subject to continued energization of the control apparatus after said program timer moves from said start position, circuit means controlled by the switch means of said power failure relay in said standby position connecting said flame detector so that a flame is simulated to cause said flame detector switching means to assume a first position indicative of the presence of flame, initial energizing circuit means for said power failure relay controlled by said flame detector switching means in said first position and by said program timer switch means in said start position and adapted to be completed upon a call for operation of the fuel burner, said power failure relay moving from said standby position to said second position upon such a call and thereby opening the circuit simulating flame to cause said flame detector switching means to assume a second condition indicative of the absence of flame, holding circuit means completed by the switch means of said power failure relay in said second position to hold said power failure relay in said second position independent of said initial energizing circuit means, initial energizing circuit means for the actuator of said program timer controlled by said flame detector in said second condition and by the switch means of said power failure relay in said second position, holding circuit means for the actuator of said program timer controlled by said timer switch means to hold said timer in operation for a starting period during which flame may be established at the fuel burner, and further circuit means controlled by the switch means of said power failure relay in standby position to hold the actuator of said timer energized after said starting period if there has been a. power failure during said starting period to cause said timer to return to start position where the power failure relay may again be energized through said initial energizing circuit and the apparatus may recycle.

9. A program burner control apparatus for use with a fuel burner comprising; a timer, an electrically-operable flame detector, control means adapted to control opera tion of a fuel burner, means controlled by said control means in a condition indicative of no need for operation of the fuel burner to simulate a flame in said flame detector, means controlled by said flame detector in a condition indicative of the presence of flame to condition said control means to be responsive to need for the operation of the fuel burner, said control means in a condition indicative of a need for operation of the fuel burner interrupting the simulation of flame in said flame detector to thereby cause said flame detector to assume a condition indicative of the absence of flame, means controlled by said control means in said condition indictive of a need for operation of the fuel burner and by said flan e detector in said condition indicative of the absence of flame to start operation of said timer, means controlled by said timer adapted to energize the fuel burner, means controlled by said timer in start position to operatively connect said flame detector to a source of power while said timer is in said start position and for a short period of operation of said timer, and means controlled by said control means in said condition indicative of a need for operation of the fuel burner to maintain said flame detector operatively connected to said source of power so long as there is a need for operation of the fuel burner.

10. A program burner control for use with a fuel burner comprising, an electronic flame detector, a timer having a plurality of switches controlled in a predetermined sequence, control means having a first condition indicative of a need for burner operation and having a second condition indicative of no need for burner operation, circuit means controlled by said control means in said second condition connecting said electronic flame detector in a manner to simulate flame, means controlled by said flame detector when in condition indicating flame to condition said control means to be responsive to need for burner operation, means controlled by said control means in said first condition and by said flame detector when in condition indicative of no flame to start operation of said timer, and means controlled by said timer switches adapted to energize the fuel burner.

11. A program burner control for use with a fuel burner comprising, an electrically operable flame detector, a timer having an electrically energizable actuator and a plurality of switches controlled in a predetermined sequence, a first of said switches closed only when said timer is in starting condition, electrically energizable control means including switching means having a first position indicative of the need for fuel burner operation and a second position indicative of no need for fuel burner operation, first circuit means controlled by the switching means of said control means in said second condition connecting said flame detector in a manner to simulate flame, second circuit means controlled by said flame detector when in condition indicative of flame and by said first switch of said timer to connect said control means to be responsive to need for burner operation, holding circuit means for said control means controlled by the switching means of said control means to hold said control means in said first condition independent of said second circuit means to insure that said control means remains responsive to need for burner operation once said control means has responded to such a need, third circuit means controlled by the switching means of said control means in said first condition and by said flame detector when in condition indicative of no flame to start operation of said timer, and means controlled by said timer switches adapted to energize the fuel burner.

12. A program burner control for use with a fuel burner comprising; means responsive to the need for burner operation, a flame detector, a timer having a start condition, control means normally controlled in accordance with a need or no need for operation of the fuel burner, means controlled by said control means while there is no need for operation of the burner to simulate a flame to thereby cause said flame detector to assume a condition indicative of the presence of flame, means controlled by said flame detector when in a condition indicative of the presence of flame and by said timer in start condition cooperating with said control means to place said control means under the control of said means responsive to the need for burner operation, means controlled by said control means when there is a need for burner operation for interrupting the simulation of flame, means controlled by said control means when there is a need for burner operation and by said flame detector when in a condition indicative of the absence of flame to initiate operation of said timer, and means controlled by said timer when said timer is no longer in start condition adapted to energize the fuel burner.

References Cited in the file of this patent UNITED STATES PATENTS 2,299,501 Schneider Oct. 20, 1942 2,313,943 Jones Mar. 16, 1943 2,440,700 Rosche May 4, 1948 2,519,889 Crawford Aug. 22, 1950 2,616,490 Wilson et a1 Nov. 4, 1952 2,710,056 Parrett June 7, 1955 

